What Is Slab?
Slab is an important structural element generally constructed horizontally to provide flat surfaces such as roof, ceiling, floor, etc. Slabs may be supported by RCC beams, columns, steel beams, etc. Basically, the depth of a slab is very small compared to its depth. There are mainly two types of slabs, i.e one way slab and two way slab. In this article, I will discuss difference between one way slab & two way slabs.
What Is One Way Slab?
One way slab is a slab which is supported by beams on the two opposite sides to carry the loads along one direction. In one way slab, the ratio of longer span (l) to shorter span (b) is equal or greater than 2, i.e Longer span (l)/Shorter span (b) ≥ 2
Example:
Verandah slab is a type of one way slab, where the slab is spanning in the shorter direction with main reinforcement and the distribution of reinforcement in the transverse direction.
One Way Slab Reinforcement Details:
In one way slab, as one side is larger than the other one, the maximum load will be conveyed by the larger side. Therefore it is important to provide adequate support to this side.
To provide adequate support to the longer side, the main reinforcement bars are provided parallelly to the shorter side and the distribution bars are provided on the longer side which won’t help in carrying the load.
In the above slab, Larger span/Shorter span = Lx/Ly = 4500/2000 = 2.5 Which is > 2.
So it is a one way slab. In this slab, the main reinforcement bars are provided on the shorter side and distribution bars are provided on the longer side.
What Is Two Way Slab?
When a reinforced concrete slab is supported by beams on all the four sides and the loads are carried by the supports along with both directions, it is known as two way slab. In two way slab, the ratio of longer span (l) to shorter span (b) is less than 2.
i.e Longer span (l)/Shorter span (b) < 2
These types of slabs are mostly used on the floor of multi-storey buildings.
Two Way Slab Reinforcement Details:
In two way slab, as the loads are carried in both directions (longer and shorter direction) main reinforcement bars are provided in both directions.
The loads are carried by two sides are equal. Slab with reinforcement in both directions is more economical than one way reinforcement slabs.
In the above slab, the ratio of longer span to shorter span
- i.e Lx/Ly = 4000/4000 = 1 Which is < 2
So it is a 2 way slab. You can see the main bars (Crank bars) are provided on both sides.
Now lets see the main differences between these two slabs.
Difference Between One Way Slab And Two Way Slab:
| One Way Slab | Two Way Slab |
|---|---|
| The slabs are supported by the beams on the two opposite sides. | The slabs are supported on all the four sides. |
| The loads are carried along one direction. | The loads are carried along with both directions. |
| The ratio of Longer span to shorter span is equal or greater than 2. (i.e l/b ≥ 2). | The ratio of Longer span to shorter span is less than 2. (i.e l/b< 2). |
| Main reinforcement is provided only in one direction (Shorter side). | Main reinforcement bars are provided in both directions. |
| The deflected shape is cylindrical. | The deflected shape is like a dish or saucer. |
Also Read
20 Types Of Slabs & Their Uses In Construction
How To Measure Height Of Building Or Tower
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good info.hey can u provide reinforcement detailing of canopy slabs?
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can u give more information in slab reinforcement
can u give more information in slab reinforcement.
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What should be the minimum reinforcement provided for column,beam and slab
Bro it depends on soil to and never think to make minimum reinforcement think of future convince you client to think of future…as per my knowledge minimum is 9×9 including concrete….everything i wrote is as per my experience……
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more details about oneway and two. way slab reinforcement.
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Now I got clear view about these two kinds of slab, it’s very important to know how it works or react on it, yes it does matter is in it……
Wow, this is really helpful. Please can you help with how to do detailing of structures. I really need it
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how can I design if the slab is one way and two way meaning combination of the two.
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Is it necessary to crank the slab reinforcement bars into the top of the supporting beams. can they be placed straight into the beam with a hook on each end??